Can I publish a book for free?

I understand the desire to get your work out to the world without having to pay upfront costs, but I'm curious about the logistics of publishing a book for free. Is there a specific platform or service that allows authors to publish their work without any financial obligation? Are there any limitations or drawbacks to publishing a book for free compared to traditional publishing methods? Additionally, how does one go about promoting a free book to ensure it reaches a wide audience?